Piston



Dec. 23, 1958 Filed March is, 1956 w. KRAMER ET AL PISTON 2 Sheets-Sheet 1 Dec. 23, 1958 w. KRAMER ET AL PISTON Filed March 19, 1956 2 Sheets-Sheet 2 401422 1 ww w n. law; A"

United States Patent 2,865,348 S QN.

Application March 19, 1956, Serial No. 572,321 Claims priority, application Germany -March 23, 1955 Claims. (Cl. 123 41.35)

This invention relates to an oil-cooled-piston for internal combustion engines. In particular, the invention is directed to, a. piston for either a stationary or vehicle mounted diesel engine.

For many years, oil-cooled pistons have been used successfully in largediesel engines. Either oil or. water is pumped through ahollow space. between the ring section and the crown of the piston head. In one-piece pistons, tubular coils have been cast in the pistons for the passage of the. cooling fluid. However, the casting of such coils with a plurality of convolutions requires considerable care, and moreover, necessitates. a special piston construction with.a large area required for the;

coils, which inmany= instances is. not desirable.

In pistons having thickened piston pin. bosses, the same have been usedto cover. theucooling space. In pistons for heavy. engines, arrangements have. beenmade for feeding. the coolant under pressure, use being made of a telescopic tube or. so-called trombone tube. In the case of high speed engines, a jointed tube is used. In medium-sized engines, the. coolant for the pistons is delivered through a bore in the connecting rod. In such constructions, elastic packings are frequently necessary in the cooling chamber of the piston when the coolant is fed under pressure. piston, into thecrank case through one or more. ports.

In small engines with cylinders having a diameter of from about 80 to 150 mm., it is difiicult to provide proper cooling for thepistonsn Although it has been attempted to direct a spray of coolant passing through a bore in the connecting rod onto the hot portions of the piston interior, nevertheless it has not been possible to direct the cooling oil into the cooling chamber precisely onto the portions in most need of cooling.

It is well known from experience that in heavily stressed engines, the temperature in the top ring groove must not exceed from 180 to 200 0, since otherwise, irrespective of the operational system of the engine, ordinary commercial lubricating oils are likely to evaporate and deposit residues in the piston ring grooves, thus preventing the correct functioning of the same. It is also known that the viscosity of a lubricating oil at 200 C. is so low that it no longer forms an elfective lubricating film. Therefore, it is necessary to provide the most eifective cooling for the top compression piston rings in the case of high-stressed plunger pistons. In small pistons, it has not heretofore been possible to feed the cooling oil in the manner customarily used in large pistons for heavy engines unless use is made of a multipart construction piston.

The objects of the instant invention are to provide a relatively small cooling chamber behind the ring section of a piston head for oil-cooled pistons in stationary and vehicle mounted diesel engines; to provide a cooling space in which there is a pulsating or intermittent flow of cooling oil; and to produce a cooling chamber in a one-piece piston.

The oil is discharged from the 2,865,348 Patented Dec. 23, 1958 In general, to. accomplish these objects, a cooling chamber is constructed in the form of a ring or annuluscomposed of thin-walled sheet metal having a higher melting point than the piston body. This annular chamber is cast in the piston adjacent the ring section at the time the one-piece piston is cast. The annular chamber can be formed by bending and compressing the metal sheets, or can be. formed by profiled bands which may be held together. by welds until they are inserted into the casting mold. The cooling oil in the tube or passages are connected to the tube or chamber in such a manner that the cooling oil first impinges on the ring section of the piston head andthen flows: over the hotter portions of the head. These feedtubes orpassages may be constructed in accordance with the advantageous forms employed in large diesel engines.

The means by. which the=objects of'the invention are obtained are described morefullywitlr reference to the accompanying drawings, in which:

Figures 1 to 6, respectively, arecross-sectional views through several embodiments of the invention.

Inall modifications, the cooling chamber 1 is composed. of a thin-walled metal sheet 2 bent to form a hollow ring which is embedded in the one-piece piston during the casting of the same. larger-thanthe volume of cooling oil it contains at any instant, so that; the. pulsating. or intermittentlyflowing oil only partially fills the chamber and is splashed'in the chamber to elfect the cooling of the piston.

As shown in Figure. 1; a plunger piston 3 for a twostroke diesel engine. has a relatively narrow cooling chamber 1 behind the. ring section 4,- said chamber be ing. in contact with the. crown 5 of :the piston head over only a small area. The. combustion pressure is transmitted partly throughnthe outer piston. cross-section, and for the. greater part, through the inner-wall 6 to the piston pin bosses 7. Oil'isintroduced through a cast-in jet :tube Sleading intochamber 1 in such a manner that the cooling-oil firstreachesthe hottest portion of thepistonhead, The length of chamber 1* parallel to the longitudinal axis ofiithe piston can be made solarge; de-

is subject to direct cooling.

In Figure 2, the piston for a four-stroke engine has a hollowed out Hesselmann type combustion chamber 9 in the piston head 10. In this type of piston, very high thermal stresses are often produced not only in the ring section, but also in the peripheral section 11 of the piston head. Cooling chamber 1, consequently, is shaped so that efiicient heat removal takes place over the entire thermally overstressed region. A thin, sharp jet of oil is supplied from the nozzle 12 secured to the crank case 13 into a bore or tube 14 cast into the piston and communicating with chamber 1, the oil being fed during the running of the engine. One or more tubes 14 can be provided for feeding cooling oil and also removing the oil from chamber 1, the tubes being arranged so that the oil discharged from chamber 1 does not wet the interior of the piston.

However, in the pistons shown in Figures 1 and 2, it is possible to permit the oil discharged from chamber 1 to flow directly into the interior of the piston through suitable bores. In addition, occasionally it is advantageous to combine simultaneously the intensive piston pin lubrication in the piston pin bosses 15 with the cooling oil tubes 14, preferably use being made of the cold feed oil. However, if the oil discharged from chamber 1 is not at a very high temperature, it can be used also for lubricating the piston pin.

The piston in Figure 3 has a spherical combustion Cooling chamber 1 is chamber 16. This type of piston has to withstand a high thermal load both in the ring section and in the portion 17 of the piston head adjacent the combustion chamber 16. Therefore, cooling chamber 1 is shaped so that the portion 17 and the ring section are cooled by oil moving to and fro in chamber 1. To increase the cooling action and to strengthen the piston head, ribs 18 extending as far as possible radially are provided on the undersurface of the piston head, a greater area of cooling surface thus being formed. In this type of piston, it is possible to introduce the cooling oil through a bore in connecting rod 19, the oil being then passed through corresponding holes 20 in the piston pin hearing 21, and then passing through cast-in tube or passage 22 communicating through hole 20 and chamber 1. Tube 22 and the corresponding discharge tubes can be extended so far into chamber 1 that when'the piston is at rest, a corresponding amount of cooling oil is retained in chamber 1.

The piston 23 in Figure 4 is not only very highly stressed in the ring section 24, but also becomes so hot in the piston head 25 that cooling of the latter is absolutely necessary. The cooling oil is supplied through the hollow bore in connecting rod 26 from which oil is supplied through nozzles 27 extending parallel to piston pin bearing 28. The oil enters chamber 1 through an arcuate or crescent-shaped slits 29 while the engine is running. Slits 29 are shaped so that with a maximum movement of about 30 of the connecting rod, the jet of oil enters chamber 1 regardless of the speed of the piston.

In order to direct the cooling oil in a suitable path in the piston of Figure 4, both vertical and radially extending ribs are provided in chamber 1. The heated 0 oil can be discharged from chamber 1 both near the center 30 of the piston head, and at right angles to the slits 29 at the lower edge of chamber 1.

In Figure 5, the piston has a double-walled skirt extending as far as the bottom scraper ring groove 31.

Cooling oil is introduced through a hollow bore in connecting rod 32. The spray nozzle 33 is located beneath the piston pin bearing 34 and parallel thereto, and introduces the oil into arcuate slit 35 having a length of about 30, said slit communicating with chamber 30 ring groove to the interior of the piston.

ton head at the end of each connecting rod stroke. The coo-ling oil can therefore be discharged from chamber 1 beneath the undersurface of combustion chamber 36 and drained back into the interior of the piston.

To provide for the greatest possible stability in pistons of this type, the cooling chamber 1 can be stifiened by partitions 37, of circular or other shape, which are inserted in the piston skirt and at points where bores are provided to return lubricating oil from the piston The partitions are constructed so that the pendulum or jolting movement of the cooling oil is not substantially affected in chamber 1.

The piston of Figure 6 has a solid skirt and a piston pin trunnion 38. The cooling oil is also provided in chamber 1 adjacent the ring section of the piston head by the jolting or pendulum movement of the oil. The oil is introduced through tube 39 or through a bore in the connecting rod. A port 40 in trunnion 38 serves to discharge the cooling oil from chamber 1 and chamber 41 beneath the piston head, the oil being drained into the crank case by way of the connecting rod.

Having now described the means by which the objects of the invention are obtained,

We claim:

1. An oil-cooled piston comprising a piston body With a piston head having a crown and a ring section, a circular sheet metal cooling oil splash chamber molded in the piston head and extending as a single opening from said crown to along at least half the length of said ring section, and oil inlet and discharge passages communicating with said chamber through said piston body for partially filling said chamber with cooling oil.

2. An oil-cooled piston as in claim 1, said oil inlet F and discharge passages comprising tubes projecting at least partially into said chamber.

3. An oil-cooled piston as in claim 1, said piston head having a combustion chamber.

References Cited in the file of this patent UNITED STATES PATENTS 2,369,906 Moore Feb. 20, 1945 2,369,907 Moore Feb. 20, 1945 FOREIGN PATENTS 195,042 Great Britain Apr. 7, 1924 

